Hand held power tools, such as finish sanders or grinders, are used for a variety of purposes. In the case of a finish sander for example, they can be used to perform specific finishing tasks such as sanding edges adjacent internal walls. To perform such tasks, finish sanders or grinders operate with controlled finite movements in a confined area so as to fine sand or grind a desired area without damaging the surrounding surfaces. Various approaches have been taken to perform the difficult task of sanding or grinding these internal corners and other hard to reach areas which require fine sanding or abrasion.
Initially, hand tools were utilized to perform these tasks. U.S. Pat. No. 4,825,597 to Mateschuk discloses such a corner hand sander. However, electrically operated tools have replaced such hand corner sanders. Such electrically driven sanders or grinders typically employ an abrasive pad which is driven in a pivotal or oscillating manner. In using such electrically driven sanders or grinders, it is desirable to be able to change the shape of the abrasive pad for different applications or to reach into different areas, such as tight crevices.
In some applications it is desirable to employ a dust collection system to collect dust resulting from the grinding or sanding process in order to minimize clean up and to prevent a build up of that dust from interfering with the grinding or sanding process.
It is especially desirable for an electrically driven sander or grinder to have removable and interchangeable pads, all of which will operate properly in conjunction with the dust collection features of such a tool. Various approaches have been taken in the past to solve these problems.
U.S. Pat. No. 4,920,702 to Kloss et al. discloses a portable grinder which relies upon pivotally oscillating a pad about a pivot axis which intersects a central region of the pad. The drive shaft of the grinding tool is externally or internally threaded and the pad is connected to the drive shaft via a nut or screw arranged in a central recess of the pad. The drive shaft also defines a central bore for the removal of dust by suction through the center of the sanding pad. Additionally, in order to ensure that dust is removed throughout the pad surface and not only centrally, grooved suction channels are provided in the working surface of the sanding pad itself.
An alternative approach is disclosed in U.S. Pat. No. 4,905,420 to Flachenecker et al. in which, similar to the portable grinder disclosed in Kloss et al., the grinding pad is held to the drive shaft by a clamping element, such as a bolt, arranged in a central recess of the pad. In order to remove dust resulting from grinding, an exhaust hood is provided which sealingly engages the upper surface of the sanding pad such that the seal is maintained while the pad is oscillated relative to the exhaust hood. Suction is applied to the exhaust hood via a suction hose. That suction collects any resulting grinding dust through openings which are provided through the pad itself.
The portable grinder arrangements disclosed in Kloss et al. and Flachenecker et al. leave several problems unsolved. First, the pads are not easily interchanged. In order to change a pad, the portable grinder must be turned upside down, the screw or nut unfastened, the pad replaced, and the screw or nut resecured. Second, by utilizing a central vacuum bore and a grooved pad as disclosed in Kloss et al., or suction openings through the pad itself as disclosed in Flachenecker et al., the effective area of the pad is greatly reduced. Furthermore, if working in a cramped space where little movement of the pad is possible, such discontinuities in the working surface of the pad will interfere with proper grinding or sanding, leaving impressions on the surface being worked between the abrasive pad surfaces and the non-abrasive discontinuities. Third, some by-product dust resulting from grinding or sanding operations is desirable between the pad and the working surface in order to provide extra abrasive material. Because the Kloss et al. and Flachenecker et al. inventions suck abrasive by-products through the pad surface itself, the by-products do not have a chance to assist the user.
Accordingly, there remains a need for a working pad tool which may be easily removed and interchanged with other tools and which, if desired, allows for the collection of dust or other debris around its periphery, and not through the working surface of the tool itself.